javascript regex detect duplicate blank lines

Question

I tried to detect duplicate blank lines with

\s*\n\n+

but doesn't seem to work with

  test1
   
    
   
   test2
   test3
  test4

  test1
   
    
   
   test2
   test3
  test4

Define "doesn't work." Keep in mind that \s* will also match newline characters. — Tim Biegeleisen
– Tim Biegeleisen, Commented Oct 14, 2022 at 11:04
@Rajesh /\n{2,}/ matches 2 or more line breaks. OP needs to match two or more blank lines. /\n[^\S]+/ matches a newline and then one or more whitespace chars (not necessarily a newline). Basically, neither is the solution. — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Oct 14, 2022 at 11:09
@WiktorStribiżew consecutive new lines would mean blank lines. Correct? — Rajesh Dixit
– Rajesh Dixit, Commented Oct 14, 2022 at 11:10
No, those are empty lines, not blank lines, see the regex demo link. — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Oct 14, 2022 at 11:10

Rajesh Dixit · Accepted Answer · 2022-10-14 11:20:38Z

3

As commented,

A simpler way would be /\n{2,}/ or /\n[^\S]+/

you can try /\n[^\S]*\n/.

Idea is to check for new line, optionally followed by whitespace character followed by a new line.

answered Oct 14, 2022 at 11:20

Rajesh Dixit

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Comments

Wiktor Stribiżew · Accepted Answer · 2022-10-14 11:08:29Z

1

You can use

\n(?:[^\S\n]*\n)+

See the regex demo. If there can be CRLF endings:

\r?\n(?:[^\S\n\r]*\r?\n)+

Details:

\r? - an optional carriage return symbol
\n - a newline char
(?:[^\S\n]*\n)+ - one or more occurrences of
- [^\S\n]* - zero or more whitespace chars excluding newline char, and then
- \n - a newline char.

answered Oct 14, 2022 at 11:08

Wiktor Stribiżew

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